Formable orthopedic fixation system with cross linking

ABSTRACT

A subcutaneously assembled in place orthopedic construct is provided, such as for fixation of the spine. The construct includes a first bar and a second bar for attachment to the spine. A crossbar connects the first and second bar, to provide additional structural support. Each of the first bar, the second bar, and the crossbar may be inserted in a minimally invasive procedure, and constructed in place to form the orthopedic device. Each of the first bar, second bar, and crossbar may comprise an inflatable container, adapted for inflation with a hardenable media and cured in place. Methods and delivery structures are also disclosed.

[0001] This is a continuation-in-part of U.S. patent application Ser.No. 09/943,636, filed on Aug. 29, 2001, which is a continuation-in-partof U.S. patent application Ser. No. 09/747,066, filed on Dec. 21, 2000,which claims priority to U.S. Provisional Patent Application 60/213,385,filed Jun. 23, 2000, entitled “Percutaneous Interbody Fusion Device,”the contents of each of which are incorporated in their entirety intothis disclosure by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to medical devices and, moreparticularly, to systems for forming orthopedic fixation orstabilization implants in place within the body, such as by infusing aformable media into a cavity. In one application, the present inventionrelates to minimally invasive procedures and devices for forming aspinal stabilization rod in situ.

[0004] 2. Description of the Related Art

[0005] The human vertebrae and associated connective elements aresubject to a variety of diseases and conditions which cause pain anddisability. Among these diseases and conditions are spondylosis,spondylolisthesis, vertebral instability, spinal stenosis anddegenerated, herniated, or degenerated and herniated intervertebraldiscs. Additionally, the vertebrae and associated connective elementsare subject to injuries, including fractures and torn ligaments andsurgical manipulations, including laminectomies.

[0006] The pain and disability related to these diseases, conditions,injuries and manipulations often result from the displacement of all orpart of a vertebra from the remainder of the vertebral column. A varietyof methods have been developed to restore the displaced vertebrae orportions of displaced vertebrae to their normal position and to fix themwithin the vertebral column. For example, open reduction with screwfixation is one currently used method. The surgical procedure ofattaching two or more parts of a bone with pins, screws, rods and platesrequires an incision into the tissue surrounding the bone and thedrilling of one or more holes through the bone parts to be joined. Dueto the significant variation in bone size, configuration, and loadrequirements, a wide variety of bone fixation devices have beendeveloped in the prior art. In general, the current standard of carerelies upon a variety of metal wires, screws, rods, plates and clamps tostabilize the bone fragments during the healing or fusing process. Thesemethods, however, are associated with a variety of disadvantages, suchas morbidity, high costs, lengthy in-patient hospital stays and the painassociated with open procedures.

[0007] Therefore, devices and methods are needed for repositioning andfixing displaced vertebrae or portions of displaced vertebrae whichcause less pain and potential complications. Preferably, the devices areimplantable through a minimally invasive procedure.

SUMMARY OF THE INVENTION

[0008] There is provided in accordance with one aspect of the presentinvention, a method of treating the spine. The method comprises thesteps of attaching a first support structure to the spine, and attachinga second support structure to the spine. A crossbar is attached to thefirst and second support structures, and at least the attaching acrossbar step comprises advancing at least a portion of the crossbarbetween the spine and a muscle layer.

[0009] In accordance with another aspect of the present invention, thereis provided a method of treating a patient. The method comprises thesteps of securing a first rod at a first site in the patient. A secondrod is secured at a second site in the patient. Curable media isintroduced in between the first and second rods to form a cross link.The first rod is linked to the second rod by permitting the media tocure.

[0010] The introducing step in one application of the inventioncomprises introducing the curable media into a tubular media supportstructure extending between the first and second rods. The supportstructure may comprise a balloon. Preferably, the method is accomplishedpercutaneously.

[0011] There is provided in accordance with a further aspect of thepresent invention, a subcutaneously assembled in place orthopedicconstruct. The construct comprises a first support structure, attachedto the spine. A second support structure is also attached to the spine.A crossbar connects the first support structure to the second supportstructure to form an orthopedic construct. The crossbar is attached tothe first and second support structures subcutaneously, without the needfor an open surgical cutdown.

[0012] The first support structure preferably comprises a hardenablemedia, and the second support structure preferably also comprises ahardenable media. The crossbar may additionally comprise a hardenablemedia. A first cross tie may be provided, to connect the crossbar to thefirst support, and a second cross tie may be provided to connect thecrossbar to the second support. Alternatively, the crossbar includes afirst aperture for receiving the first support and a second aperture forreceiving the second support.

[0013] At least the first support structure and, in some applicationsboth the first and the second support structure comprises an outer wall,defining a cavity therein. A plurality of reinforcing fibers arepositioned in the cavity, and a hardenable media for bonding with thereinforcing fibers is provided in the cavity to form the supportstructure. The hardenable media may be hardened while the supportstructure is positioned within the body of a patient, to create anorthopedic construct.

[0014] The hardenable media comprises an epoxy, a polyurethane, or othercurable material. The reinforcing fibers may comprise carbon fibers,stainless steel or other reinforcing fibers.

[0015] In one application, the reinforcing fibers comprise graphitefibers having a diameter within the range of from about 0.003 inches toabout 0.007 inches. The reinforcing fibers may be provided in at leastone bundle, having within the range of from about 3,000 to about 12,000fibers.

[0016] The reinforcing fibers may have a tow tensile strength within therange of from about 5,000 MPA to about 7,000 MPA. The reinforcing fibersmay have a tow tensile modulus within the range of from about 250 GPA toabout 350 GPA. Preferably, at least one reinforcing sleeve is providedwithin the cavity.

[0017] Further features and advantages of the present invention willbecome apparent to those of skill in the art in view of the detaileddescription of preferred embodiments which follows, when consideredtogether with the attached claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a side elevational view of a delivery catheter having aninflatable fixation device thereon.

[0019]FIG. 2 is a cross-sectional view taken along the line 2-2 of thedelivery catheter of FIG. 1.

[0020]FIG. 3 is a side elevational cross section of a proximal portionof the delivery catheter of FIG. 1.

[0021]FIG. 4A is a side elevational cross section of a distal portion ofthe delivery catheter of FIG. 1.

[0022]FIG. 4B is a detailed view of the inflatable fixation device ofFIG. 4A.

[0023]FIG. 4C schematically illustrates a cross-section through acomposite formable rod in accordance with one aspect of the presentinvention.

[0024]FIG. 5 is a side elevational view of the inflatable fixationdevice of FIG. 1.

[0025]FIG. 6 is a cross-sectional view through the inflatable fixationdevice of FIG. 5, in the expanded position.

[0026]FIG. 7A is a schematic cross-sectional view of a valve of theinflatable fixation device of FIG. 6.

[0027]FIG. 7B is a schematic cross-sectional view of an alternate valve.

[0028]FIG. 7C is an end view of the valve of FIG. 7B.

[0029]FIG. 8 is a perspective view of the manifold of the deliverycatheter of FIG. 1.

[0030]FIG. 9 is a side elevational view of a portion of the spine,having a formable orthopedic fixation system implanted therein.

[0031]FIG. 10 is a side elevational view of a bone anchor.

[0032]FIG. 11 is a side elevational view of the bone anchor of FIG. 10,rotated 90° about its longitudinal axis.

[0033]FIG. 12 is a longitudinal cross-sectional view of the bone anchorof FIG. 11.

[0034]FIG. 13 is a side elevational view of an alternative embodiment ofa bone anchor, with bone ingrowth apertures.

[0035]FIG. 14 is a side elevational view of a screwdriver.

[0036]FIG. 15 is a side elevational view of an alternative embodiment ofa screwdriver.

[0037]FIG. 16 is a side elevational view of a guidewire directingdevice.

[0038]FIG. 17 is a top plan view of a directing sheath.

[0039] FIGS. 18-28 are partial cross-sectional midline sagittal views ofa portion of a vertebral column showing an implantation method of thepresent invention.

[0040]FIG. 29 is a posterior elevational view of a portion of avertebral column post-procedure, with two fixation devices mountedthereon.

[0041] FIGS. 30-32 are posterior elevational views of a portion of avertebral column showing a method of the present invention using adirecting sheath.

[0042] FIGS. 33 is a side elevational view of a cross tie held inposition by a cross tie deployment system, in-between a first and asecond pedicle screw.

[0043]FIG. 34 is a side elevational view as in FIG. 33, illustrating aninflatable connection rod inflated between the first and second pediclescrews, with a cross tie mounted thereon.

[0044]FIG. 35 is a posterior elevational view of a portion of avertebral column, post procedure, with two inflatable connection rodsand one crossbar mounted thereon.

[0045]FIG. 36 is a perspective, schematic view of various components ofthe cross tie system.

[0046]FIG. 37 is a perspective view of a cross tie.

[0047]FIG. 38 is a side elevational view of a portion of a spine, havingan alternate crossbar connected to an inflatable connection rod.

[0048]FIG. 39 is a posterior elevational view of a portion of avertebral column, showing the crossbar of FIG. 38.

[0049]FIG. 40 is a side elevational perspective view of a tubularcrossbar sheath.

[0050]FIG. 41 is a side elevational schematic view of the crossbarsheath of FIG. 40, mounted on a deployment catheter.

[0051]FIG. 42 is a schematic perspective view of the crossbar deploymentsystem of FIG. 41, positioned within two pairs of opposing pediclescrews.

[0052]FIG. 43 is a partial cutaway side elevational view of a sheath asin FIG. 40, having an inflatable balloon positioned therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0053] Although the application of the present invention will bedisclosed primarily in connection with a spinal fixation procedure, themethods and devices disclosed herein are intended for use in any of awide variety of medical applications where formation of an attachment,bulking, support, fixation or other element in situ may be desirable.

[0054] One advantage of the in situ prosthesis formation in accordancewith the present invention is the ability to obtain access to atreatment site through a minimally invasive access pathway, whileenabling the formation of a relatively larger implant at the treatmentsite. This allows procedure morbidity to be minimized, since opensurgical cutdowns or other invasive access procedures may be avoided. Inaddition, the in situ formation in accordance with the present inventionallows the formation of an implant having any of a wide variety ofcustomized or predetermined shapes, due to the ability of the infusiblehardenable media to assume the shape of the cavity or flexible containerinto which it is infused.

[0055] The methods and devices of the present invention additionallyenable access to a treatment site within the body along a curved andeven tortuous pathway, through which a preformed prosthesis would notfit or would not be navigable. The detachable inflatable prosthesis ofthe present invention, removably coupled to the distal end of anelongate flexible tubular catheter body, can be dimensioned forpercutaneous, surgical or transluminal advancement and deployment of aninflatable or otherwise curable in place prosthesis in any of a widevariety of orthopedic applications, such as the spine as disclosed ingreater detail below, as well as long bones, short bones, and associatedligaments and tendons. In addition, the deployment catheter andprosthesis can be dimensioned for transluminal navigation throughout thecardiovascular system, the gastrointestinal tract, the biliary tract,the genitourinary tract, or the respiratory tract (e.g. thetracheobronchial tree). The device may thus be advanced throughartificial access pathways as well as naturally occurring lumens andhollow organs. Additional applications of the in situ device formationtechnology of the present invention will become apparent to those ofskill in the art in view of the disclosure herein.

[0056] In connection with spinal fixation applications, the presentinvention involves inserting one or two or more bone anchors having aconnector such as a portal into at least a first and a second adjacentor nonadjacent vertebra An implantable, inflatable orthopedic device isinserted through the portals and inflated to lock to the bone anchorsand stabilize the bone components. A deployment system, comprising adelivery catheter removably carrying the implantable device, isprovided, such that the procedure may be conducted in a percutaneous orminimally invasive manner to minimize procedure trauma to the patient.

[0057] The deployment system shown in FIG. 1 comprises a deliverycatheter 100 which deploys the implantable inflatable orthopedic device102. Delivery catheter 100 preferably includes an elongate, flexibletubular body 104, having a proximal end 106 and a distal end 108. Forcertain applications, however, in which direct linear access isintended, the tubular body 104 may be substantially rigid. The tubularbody 104 includes one or more passages or lumens extending axiallythrough the body, depending upon the desired functionality of thedevice.

[0058] The overall length and cross sectional dimensions of the deliverycatheter 100 may be varied, depending upon the intended clinicalapplication. In a device intended for percutaneous or minimally invasivefusion of lumbar and/or sacral vertebrae, for example, the tubular body104 will generally have a length within the range of from about 15 cm toabout 30 cm, and a diameter within the range of from about 2 mm to about3 mm.

[0059] Percutaneous insertion of the delivery catheter 100 may befacilitated by the provision of a removable elongate stiffening wire122, extending through a lumen such as inflation lumen 130 (see FIG. 2)from the proximal end 106 of tubular body 104, to the distal end 108 oftubular body 104. Optionally, the stiffening wire 122 extends into, andeven all the way to the distal end 118 of the orthopedic device 102, toprovide support and column strength to the device 102 which may bedesirable during tissue penetration.

[0060]FIG. 2 shows a cross-sectional view through the elongate body 104,showing (not to scale) an inner sleeve 110 and an outer sleeve 112. Theinner sleeve 110 defines a first, inflation lumen 130, while a second,venting lumen 132 is defined by the annular space between the innersleeve 110 and outer sleeve. 112. The inflation lumen 130 is adapted toreceive the elongate stiffening wire 122 in a sliding fashion through aproximal opening 127 on inner sleeve 110, which in turn extends axiallyinto the outer sleeve 112 by way of port 126 in catheter manifold 124.Although the illustrated embodiment has a dual lumen, concentric orcoaxial configuration, three or more lumen may alternatively beprovided, depending upon the desired capabilities of the catheter. Asingle lumen catheter may also be provided, to accommodate a removablestiffening wire, if utilized, and to facilitate inflation of theimplantable device. Alternatively, a two or more lumen catheter shaftmay be fabricated, extruded or otherwise formed with the lumen in aside-by-side configuration.

[0061] The deployment device 100 further comprises a manifold 124,located at the proximal end 106 of the elongate tubular body 104. Thecatheter manifold 124 provides a maneuvering handle for the health careprofessional, and supports an inflation port 126 and a vent port 128.Either or both the inflation port 126 or the vent port 128 may beprovided with a coupling, such as a luer-lock fitting for connection toassociated devices as is known in the art. For example, a luer or otherconnector on the inflation port 126 facilitates connection to a sourceof pressurized inflation media in a conventional manner. The vent port128 may be connected to a syringe or other device to draw a vacuum, toevacuate air from the balloon prior to infusion of the hardenable media.

[0062] The manifold 124 may also include an injection port for allowinginjection of radiopaque contrast fluid to enable visualization of thedelivery device on a fluoroscope. The proximal manifold 124 may bemachined or injection molded of any of a variety of known suitablematerials such as PTFE, nylon, polyethylene, or others known in the art.A precision gasket may also be provided, which seals securely around theinner sleeve 110, prohibiting fluid loss.

[0063] Catheter manufacturing techniques are generally known in the art,including extrusion and coextrusion, coating, adhesives, and molding.The catheter of the present invention is preferably made in aconventional manner. The elongate shaft of the catheter may be extruded,using polymers such as Nylon, PEBAX, PEEK, PTFE, PE or others known inthe catheter arts, the stiffness of which may be selected asappropriate. Material selection varies based on the desiredcharacteristics. The joints are preferably bonded. Biocompatibleadhesives or heat bonding may be used to bond the joints. The balloonand stent are also made in a conventional manner.

[0064] The deployment system 100 further comprises an implantableinflatable orthopedic device 102, which may function, in a spinal fusionapplication, as an inflatable or formed in place fixation plate or rod.Implantable device 102 is removably carried by the distal end of thetubular body 104, such that inflation lumen 130 is in communication withthe interior cavity 146 of the inflatable device 102. The inflationmedia may thus be infused through inflation port 126 (or opening 127)located at manifold 124 to fill the cavity 146.

[0065] The implantable device 102, which may be a balloon 114, includesa proximal end 116, a distal end 118, and a flexible wall 148. Theballoon 114 may be formed from any of a variety of polymeric materialswhich are known in the balloon angioplasty arts. These include, forexample, complaint materials such as polyethylene, polyethylene blendsor nylon, and substantially noncompliant materials such as polyethyleneterephthalate. Any of a wide variety of other biocompatible polymers maybe utilized, as will be apparent to those of skill in the art in view ofthe disclosure herein.

[0066] The balloon 114 may comprise a single or multiple layers,depending upon the desired physical properties. In one embodiment, theballoon comprises two layers, having a reinforcing structure such as astent or a plurality of axially extending support strips sandwichedtherebetween. In an alternate embodiment, the balloon 114 comprises afirst, inner layer which restrains the hardenable media. A second, outerlayer is coaxially disposed about the first layer, and is provided witha plurality of apertures or a microporous structure. An infusion lumenis provided in the elongate tubular body, for providing communicationbetween a proximal infusion port and the space in between the inner andouter balloon layers. In this manner, fluids, which may contain any of avariety of medications, can be infused into the tissue surrounding thetreatment site. Suitable structures and manufacturing considerations aredisclosed in U.S. Pat. No. 5,295,962 to Crocker et al., the disclosureof which is incorporated in its entirety herein by reference.

[0067] Although a cylindrical configuration for balloon 114 isillustrated herein, any of a variety of alternative cross sectionalconfigurations may be utilized. The overall length, diameter and wallthickness of the implantable inflatable orthopedic device 102 may bevaried, depending on the particular treatment and access site. In oneembodiment, device 102 has an inflated length between about 2 and 12 cm,and often between about 5 cm and about 8 cm for adjacent vertebraefixation. The device 102 has an inflated diameter of generally betweenabout 0.5 and 2 cm.

[0068] The length of the balloon 114 is based upon the anticipateddistance between the first and second anchors, or, in an embodimenthaving more than two anchors, between the anchors having the greatestaxial separation. For example, in a fusion application in which twoadjacent lumbar vertebrae (e.g. L4-L5) are to be fused in an adult, thefirst and second anchors will generally be spaced apart by a distancewithin the range of from about 5 cm to about 8 cm. Preferably, the axiallength of the balloon 114 is sufficiently longer than the inter anchorspacing to permit a portion of the balloon to expand on the “far” sideof the anchor aperture as is illustrated, for example, in FIG. 9. Thus,balloon lengths for the above identified inter anchor distances willgenerally exceed the sum of the inter anchor distance and the anchordiameters by at least about 0.5 cm. Preferably, the balloon extends atleast about 1 cm beyond the portals.

[0069] For use in an application where a first vertebrae is attached toa second vertebrae, and the second vertebrae is separated from the firstvertebrae by at least a third vertebrae, for example in the lumbarspine, the inter anchor distance will generally be within the range offrom about 10 cm to about 20 cm. As will be appreciated by those ofskill in the art, in a three or more vertebrae fixation, theintermediate vertebrae or vertebraes will normally but need notnecessarily be connected to the inflatable balloon 114. Thus, in oneapplication, the balloon 114 connects a first attachment point at afirst bone and a second attachment point at a second bone, with one ormore intermediate bones unconnected to the balloon 114. In anotherapplication, at least a third anchor is provided in between the firstand second anchors, and the balloon 114 is threaded through an apertureon each of the first, second and third anchors. The desirability ofattaching or leaving unattached intervening vertebrae or other bones orstructures between two attachment points is a matter of clinicaljudgement, in view of the particular circumstances of the patient.

[0070] The primary function of the balloon 114 is to influence orcontrol the shape of the hardenable media, following injection therein.The implantable balloon 114 is not normally required to restrainpressure over an extended period of time. Thus, a greater designflexibility may be permitted, compared to conventional angioplasty orother dilatation balloons. For example, the balloon 114 may be porous,either for drug delivery as has been discussed, or to permitosteoincorporation and/or soft tissue ingrowth.

[0071] Certain hardenable media which may be utilized in connection withthe present invention, such as PMMA, have a significantly greaterviscosity in the precured form, compared to conventional angioplastyballoon inflation media. In addition, since the balloon 114 is notintended to contain significant pressure, conventional high strengthmaterials such as for high pressure angioplasty may not be necessary.This allows the balloon 114 to be constructed in any of a variety ofways, including techniques utilized for balloon angioplastyapplications. In addition, the balloon 114 (or balloon-like structure)may be made out of any of a wide variety of woven or nonwoven fibers,fabrics, metal mesh such as woven or braided wires, and carbon.Biocompatible fabrics or sheet material such as ePTFE and Dacron® mayalso be used.

[0072] The hardenable media is preferably a rapid setting, liquidpolymer or polymer precursor, such as polymethyl methacrylate. However,any of a variety of other materials which provide the requiredstiffening or setting characteristics may be used, including any of avariety of epoxies, polyurethane or blends of polyurethane-silicone.

[0073] In the context of a rod shaped inflatable container, for use inspinal fixation procedures, the physical requirements of the hardenablemedia will depend upon the length and diameter of the rod as well as thephysical requirements imposed by the implantation site. For certainembodiments, polymethyl methacrylate, epoxy, polyurethane or otherparticular material may or may not exhibit sufficient physicalproperties. Physical properties of hardenable materials can be modifiedthrough the addition of any of a variety of additives, such as carbonfibers, Kevlar or Titanium Rods, woven or laser etched metallictubular-stents, or other strength enhancers as will be understood in theart. The selection of a particular hardenable media, as well as thedesirability of adding strength, flexibility, or other physical propertyenhancers, can be optimized for any particular implantation systemthrough routine experimentation by those of skill in the art in view ofthe disclosure herein.

[0074] Certain composite materials, such as carbon fibers embedded in abonding agent such as a two part epoxy, or two part polyurethane havebeen found particularly useful in forming the implant of the presentinvention. For example, graphite (carbon fibers) having a diameterwithin the range of from about 0.003 to about 0.007 inches are providedin bundles (tows) composed of from about 3,000 to about 12,000 fibers.One typical fiber useful for this purpose is manufactured by HexcelCarbon Fibers, Salt Lake City, Utah, Part No. HS/CP-5000/IM7-GP 12K.Preferably, the Tow tensile strength is in the range of from about 5,000to about 7,000 Mpa. Tow tensile modulus is within the range of fromabout 250 to about 350 Gpa.

[0075] In general, the composite rods in accordance with the presentinvention will exhibit a static compression bending values (per ASTMF1717) within the range of from about 100 to about 200 lbs., and,preferably greater than about 150 lbs. The composite rods will exhibit astatic torsion (per ASTM F1717) within the range of from about 300 toabout 500 inch pounds, and, generally in excess of about 400 inchpounds. The rods will preferably reach at least about 5 million cycles,at 5 Hz. Each of these parameters may be measured in accordance with theprotocols described in the American Society for Testing and Materials(ASTM) designation F 1717-96, a copy of which is attached hereto asAppendix A, and which is incorporated in its entirety herein byreference.

[0076] Within the range of from about 30 to about 60 bundles of thecarbon fiber described above is packed in a deflated balloon, along witha Ni-Ti stent having an 8 mm diameter and 8 cm length. Although any of avariety of stents may be utilized, one useful structure is similar tothe Smart Stent (Cordis), and it helps keep the structure intact andalso adds structural strength to the implanted structure.

[0077] A one or a two part epoxy having a viscosity in the range of fromabout 100 to about 500 cps is then injected into the balloon underpressure such as by using a pump and pressure within the range of fromabout 4 ATM to about 10 ATM or more depending upon viscosity, balloonstrength and other design considerations. The pump is run for asufficient duration and under a sufficient pressure to ensure that theepoxy wets all of the fibers. This may range from about 10 minutes ormore to about an hour, and, in one application where the pump was run atabout 5 ATM pressure, requires at least about 12 hour. Specific methodparameters may be optimized depending upon the viscosity of the epoxy,infusion pressure, infusion flow rate, density of the packed carbonfibers, and other variables as will be apparent to those of skill in theart in view of the disclosure herein.

[0078] In an alternate embodiment, carbon fibers having within the rangeof from about 15 to about 45 degrees of braids are utilized. The braidmay be in the form of a plain weave, and may be obtained, for example,from Composite Structures Technology (Tehachapi, California). A 0.5 inchdiameter of 45 degrees braided carbon fiber sleeve is positioned withinthe center of the balloon. This braided sleeve conforms dimensionally tothe inside diameter of the balloon. A 0.3 inch diameter braided carbonsleeve (again 45°×45° plain weave) is positioned concentrically withinthe balloon, within the outer braided carbon fiber sleeve.Unidirectional fibers are thereafter introduced inside of the ID of theinner braided carbon sleeve. Unidirectional fibers are also introducedinto the annular gap between the two braided sleeves. The volume of thefiber per volume of balloon is generally within the range of from about40% to about 55%. After placement of the foregoing structure within theportals of the screws, the epoxy mix having a viscosity within the rangeof from about 500 to about 1000 cps is injected under 10 atmospherespressure into the balloon.

[0079] Although the foregoing composite structure was described using acarbon fiber example, any of a variety of fibers may be positionedwithin the balloon to enhance the physical properties of the finishedproduct. For example, Kevlar fibers, PEEK, and any of a variety ofalternatives may be used. In general, the fibers will preferably providea very high tensile strength and high modulus, having a low diameter toenhance deliverability of the device.

[0080] The use of braided sleeves will produce higher structuralresistance to sheer stress as a result of torsional loads, plus theability to distribute unidirectional fibers in a homogenous mannerwithin the balloon at all times. This appears to improve the performanceof the implant.

[0081] One construction of a composite formable rod in accordance withthe present invention is illustrated in FIG. 4C. An outer balloon orother containment structure 114 is provided, as has been discussed. Areinforcing element 120 such as a stent is concentrically positionedwithin the balloon. An outer support tube 121 is positioned within thestent in the illustrated embodiment, however, the outer support tube 121can alternatively be positioned concentrically outside of the stent 120.The outer support tube 121, in one embodiment, is a 0.5 inch diameterbraided carbon fiber tube, having cross stands oriented at 45° angleswith respect to each other to improve torsion resistance as has beendiscussed.

[0082] An inner support tube 123 is spaced radially inwardly from theouter support tube 121. Inner support tube 123, in one embodiment,comprises a 0.3″ diameter braided carbon fiber sleeve havingcharacteristics described above. A first plurality of unidirectionalfibers 125 is axially oriented within the annular space between theouter support tube 121 and inner support tube 123. A second plurality ofunidirectional carbon fibers 127 is positioned within the inner supporttube 123.

[0083] Any of a variety of alternate constructions can be readilyutilized, in accordance with the teachings herein. For example, three ormore tubular support tubes may be utilized. The layering sequence of thevarious components may be changed, and other features added or deleteddepending upon the desired performance of the finished device. Inaddition, although the balloon 114 in one embodiment comprises a nylonsingle layer balloon, other materials may be utilized. In addition,multiple layer balloons may be utilized, with or without supportstructures such as stents, wires, or woven tubular support structuressandwiched therebetween.

[0084] Marker bands made of materials such as gold, platinum or tantalummay also be positioned on the balloon, to facilitate fluoroscopicvisualization. Alternatively, a radio opaque material, such as tantalumpowder, may be sprinkled among the carbon fibers prior to infusion ofthe epoxy or other hardenable media, to allow visualization duringplacement.

[0085] The epoxy or the polyurethane material preferably has arelatively fast cure rate at 37° C. A low viscosity (no greater thanfrom about 100 to about 1000 CPS) facilitates rapid transluminalintroduction through the delivery catheter and wetting of the relativelysmall intrastitial spaces between adjacent carbon fibers. In addition,the polymer is preferably radiopaque. The polymerization is preferablyminimally exothermic, to minimize or prevent thermal damage to thesurrounding tissue. One epoxy which may be useful in the presentinvention is Epotek 301. This epoxy reaches 50 to 60% of its strengthwithin about three to four hours following deployment, at 37° C. Using abonding agent having these approximate characteristics, the patient canbe restrained from rolling for an initial cure period of approximatelythree or four hours to achieve a partial cure (e.g., at least about 50%and preferably 60% or more), and be maintained in bed for a secondarycure period such as approximately the next eight to twelve hours or moreto accommodate a full cure. Other formulations of two part epoxies orpolyurethanes with faster cure times (preferably no more than about onehour full cure) can be formulated by changing the ratios of componentsand formulations for the catalysts.

[0086] Terms such as “hardenable” or “curable” media are usedinterchangeably herein, and are intended to include any material whichcan be transluminally introduced through the catheter body into thecavity 146 while in a first, flowable form, and transitionable into asecond, hardened form. These terms are intended to cover materialsregardless of the mechanism of hardening. As will be understood by thoseof skill in the art, a variety of hardening mechanisms may exist,depending upon media selection, including UV, other wavelength ofelectromagnetic energy, or catalyst initiated polymerization, thermallyinitiated polymerization, solvent volatilization, and the like. Whilethe media selection may affect catheter design in manners wellunderstood by those of skill in the art, such as to accommodateoutgasing of byproducts, application of heat, catalysts, or otherinitiating or accelerating influences, these variations do not departfrom the concept of the invention of introducing a flowable media into ashape and subsequently curing the media to the shape. Two part medias,such as a two part epoxy or polyurethane, or a monomer and an initiatormay be introduced into the cavity 146 through separate lumen extendingthroughout the tubular body. Expandable media may also be provided, suchas a material which is implantable in a first, reduced volume, and whichis subsequently enlargeable to a second, enlarged volume such as by theapplication of water or heat, or the removal of a restraint.

[0087] Various safety features to minimize the risk of rupture orleakage of the hardenable media may be utilized, depending upon designpreferences. For example, a two-layer or three-layer or more balloon maybe utilized to reduce the risk of rupture. In addition, the material ofthe single or multiple layers of the balloon may be selected to minimizeescape of volatile components from the curable media. In one embodiment,a double balloon is provided having a nylon inside layer and a PEToutside layer.

[0088] In addition, the inflation pressure of the curable media may beaffected by the nature of the balloon. For example, a polyethyleneballoon having a wall thickness of about 0.001″ may have a burstpressure of about 7 to 8 atmospheres. In that embodiment, an inflationpressure of no more than about 4 to 5 atmospheres may be desired. Aslightly higher inflation pressure, such as on the order of from about 5to about 6 atmospheres, may be utilized with a nylon balloon. Relativelynoncompliant materials such as PET have much higher burst pressures(range of 10-20 atmospheres), as is well understood in the balloonangioplasty arts.

[0089] In addition, the balloon contains a proximal valve as will bediscussed in additional detail below. Multiple valves may be utilized,in series along the flow path, to reduce the risk of failure and escapeof hardenable media. As a further safety feature, the deploymentcatheter may be provided with an outer spill sheath in the form of anelongate flexible tubular body which surrounds the deployment catheterand at least a proximal portion of the balloon. This spill sheathprovides an additional removable barrier between the junction of thecatheter and the balloon, and the patient. If a spill occurs during thefilling process, the spill sheath will retain any escaped hardenablemedia, and the entire assembly can be proximally retracted from thepatient. Following a successful filling of the balloon, the spill sheathand deployment catheter can be proximally retracted from the patient,leaving the inflated formable orthopedic fixation structure in place.

[0090] The reinforcing element 120 may be exposed to the interior cavity146 formed by the flexible wall 148, providing additional structuralintegrity. See, e.g., FIGS. 1 and 4C. The reinforcing element 120resists kinking of the balloon as the balloon is advanced around cornerssuch as during advancement through an aperture (e.g., portal or eyelet)on a bone anchor. The reinforcing element 120 may be positioned withinthe balloon 114. The reinforcing element may alternatively be embeddedwithin the wall of the balloon 114, or carried on the outside of theballoon much like a conventional stent. The reinforcing element 120 maybe an expandable tube; a slotted metal tube, reinforcing wires,straight, woven or braided fibers such as carbon fibers, or a stent.Certain preferred embodiments may include a tube and wire. Reinforcementelement 120 may comprise thin, reinforcing metallic wires, separate fromthe balloon wall. The wires increase the tensile strength of balloon 114when inflated. Wires may be titanium, nitinol, elgiloy, or any othersuitable material as known to those of skill in the art.

[0091] The reinforcement element 120 may include an expandable tubularstent. A stent of any suitable type or configuration may be providedwith the delivery device, such as the Cordis artery stent (“smartstent”). Various kinds and types of stents are available in the market(Sulzer/Medica “Protege” stent and Bard “Memotherm” stent), and manydifferent currently available stents are acceptable for use in thepresent invention, as well as new stents which may be developed in thefuture.

[0092] Referring to FIGS. 4A and 4B, the illustrated elongate tubularbody 104 comprises an outer sleeve 112 and an inner sleeve 110 movablypositioned within the outer sleeve 112. The inflatable device 102 isremovably carried by or near the distal end 108 of the outer sleeve 112.Alternatively, the inflatable device 102 may be removably carried by theinner sleeve 110. The inner sleeve 110 may extend into the inflatabledevice 102, as illustrated.

[0093] The balloon 114 may be removably attached to the tubular body 104by a slip or friction fit on the distal end 108 of the outer sleeve 112or on the inner sleeve 110. A variety of alternative releasableattachments may be used between the outer sleeve 112 and/or inner sleeve110 and the proximal end 103 of the balloon 114, such as threadedengagement, bayonet mounts, quick twist engagements like a luer lockconnector, and others known in the art. In each of these embodiments, afirst retention surface or structure on the outer sleeve 112 and/orinner sleeve 110 releasably engages a complimentary surface or retentionstructure on the proximal end 103 of the balloon 114 as will be apparentto those of skill in the art.

[0094] The balloon 114 comprises a self-sealing valve 160 which preventsthe hardenable media from leaking once the delivery catheter 100 isdetached from the balloon 114. Valve 160 is provided for closing thepathway between inflation lumen 130 and inner cavity 146. Valve 160 maybe located at the proximal end 116 of inflatable device 102. A varietyof different valves may be used as will be recognized by those of skillin the art, such as a slit valve, check valve, duck-billed or flapvalve. Alternatively, a stopper may be provided which can be placedwithin the pathway to prevent leakage.

[0095] Referring to FIG. 7A, a duck bill valve is schematicallyillustrated. This valve includes at least a first, and preferably two ormore coaptive leaflets 161 and 163, which incline towards each other inthe distal direction as will be understood by those of skill in the art.Distal advancement of the inner sleeve 110 and/or pressurized mediathrough the valve 160 forces the coaptive leaflets 161 and 163 apart, tofacilitate introduction of the hardenable media. Upon removal of theinner sleeve 110, the coaptive leaflets 161 and 163 return to a closedconfiguration to inhibit or prevent the escape of hardenable media. Asingle leaflet 161 may be utilized, in the form of a flapper valve.

[0096] An alternate valve is illustrated in FIGS. 7B and 7C, and in anassembled device in FIG. 4B. In this valve, a tubular support structure165 is provided with a closeable cap 167. The closeable cap 167 may beformed from any of a variety of highly flexible polymeric materials,such as silicone, neoprene, latex, or others known in the art. Cap 167may be formed such as by dip molding or liquid injection molding,followed by the provision of a slit or potential opening 169.

[0097] The valve 160 may be connected to or formed with the inflatabledevice in any of a variety of manners, as will be appreciated in view ofthe disclosure herein. In the illustrated embodiment, the balloon 114 isprovided with a proximally extending neck 115 which carries the valve160 therein. The tubular body 165 having the cap 167 thereon ispositioned concentrically within the proximal neck 115, as illustratedin FIG. 4B. Alternatively, the valve 160 may be positioned within theballoon 114, i.e., distally of the proximal shoulder of the balloon 114.

[0098] Additional details of one detachable connection between thedelivery system and the implantable device is illustrated in FIG. 4B. Asillustrated therein, a tube 161 extends distally from the outer sleeve112. Tube 161 may comprise any of a variety of materials, which exhibitsufficient structural integrity for the intended use. In one embodiment,tube 161 is a metal hypotube having an inside diameter of about 0.085″to about 0.086 and a wall thickness of about 0.001″ to about 002″. Thetube 161 in the illustrative embodiment extends for a distance of about0.50 mm to about 0.75 mm beyond the distal end of the outer sleeve 112.

[0099] The tube 161 extends into a sliding fit with a tubular supportstructure 163 which may be positioned in a proximal neck portion of theballoon. When positioned as illustrated, the tube 161 ensures that thevalve 160 is open, so that the inner sleeve 110 may extend axiallytherethrough into the balloon.

[0100] In addition, the inside diameter of the tube 161 is preferablysufficiently larger than the outside diameter of the inner sleeve 110 toprovide an annular passageway in communication with the vent lumen 132.This structure ensures that the interior of the balloon remains incommunication with the proximal vent port by way of a vent lumen 132extending throughout the length of the assembly. In the illustratedembodiment, the outside diameter of the inner sleeve 110 is about 0.082″to about 0.084″, and the inside diameter of the tube 161 is about 0.085″to about 0.086″. Following infusion of the curable media into theballoon, the inner tube 110 and tubular body 161 are both proximallyretracted from the balloon, thereby enabling the valve 160 to close asis described elsewhere herein.

[0101] When fully inflated, as shown in FIG. 6, the balloon 114 has aninflated profile with a cylindrical working portion 140 having aninflated diameter located between a pair of conical end portions 142,144.

[0102] Referring to FIG. 9, at least one bone anchor 10 may be provided,such as that shown in FIG. 10. The bone anchor 10 includes a firstaperture 22, through which the orthopedic device 102 extends. A secondbone anchor 10 may also be provided including a second aperture 22,through which the orthopedic device 102 also extends. The first boneanchor 10 is preferably implanted within a first bone. The second boneanchor 10 may be implanted within the second bone. The bones may beadjacent vertebrae or first and second vertebrae spaced apart by one ortwo or more intermediate vertebrae.

[0103] The bone anchors of FIGS. 10-13 are made of a biocompatiblematerial such as titanium or stainless steel. Alternatively, boneanchors 10 may be made of a composite material. Bone anchors 10 may alsobe made of a suitable medical grade polymer. In one embodiment, boneanchors 10 have a length between about 40 mm and 60 mm, preferably about50 mm. However, the actual length is dependent on location of thefracture, size of patient, etc.

[0104] Bone anchor 10 comprises a proximal portion 12 having a proximalend 14 and a distal portion 16 having a distal end 18. Proximal portion12 typically comprises a head 20 and a portal 22. In a preferredembodiment, head 20 comprises a proximal portion 24 configured to matewith the tip of a screwdriver. Head 20 may comprise a standard orPhillips slot for mating with the screwdriver. A variety of slotconfigurations are also suitable, such as hexagonal, Torx, rectangular,triangular, curved, or any other suitable shape. The bone anchor of FIG.13 has a raised platform 25 having a plurality of substantially straightsides, such as a hexagonal platform, configured to mate with acorresponding depression in the distal end of a screwdriver. Platform 25may come in a variety of shapes suitable mating with a screwdriver.

[0105] Portal 22 of bone anchor 10 may extend through head 20 and isgenerally between about 4 mm and 8 mm in diameter, preferably about 6 mmto about 8 mm in diameter. Portal 22 may be of any shape suitable forreceiving inflatable, implantable orthopedic device 102; however, portal22 is preferably round.

[0106] Distal portion 16 of bone anchor 10 typically comprises threads26 and a sharp tip 28. Bone anchor 10 also preferably comprises acentral lumen 30 extending coaxially completely through bone anchor 10from proximal end 14 to distal end 18 and configured to receive aguidewire. Bone anchor 10 may also include at least one perforation 32,as shown in FIG. 14. Perforation 32 may be aligned axially, as shown, ormay be staggered axially. Perforation 32 permits bone to grow into boneanchor 10, stabilizing bone anchor 10 within the bone. Additionally,bone matrix material such as a hydroxyapatite preparation can beinjected into central lumen 30 and through perforation 32 to promotebone in-growth.

[0107]FIGS. 14 and 15 show screwdrivers 40 configured to apply torque tobone anchor 10. Screwdriver 40 comprises a proximal portion 42 having aproximal end 44 and a distal portion 46 having a distal end 48. Proximalportion 42 includes a handle 50 configured to permit grasping to applytorque to anchor 10. Various configurations of proximal end 44 arepossible. In the embodiment of FIG. 15, the proximal handles 50 may beindependently rotatable about their longitudinal axes.

[0108] Distal portion 46 comprises a shaft 52 having a tip 54 configuredto interface with proximal portion of bone anchor 10. Screwdriver 40 mayalso comprise a central lumen 55 extending coaxially from proximal end44 to distal end 48 configured to receive a guidewire.

[0109]FIG. 16 shows a guidewire directing device 60, which may be usedpercutaneously to alter the direction of an advancing guidewire.Guidewire directing device 60 comprises a proximal portion 62 having aproximal end 64 and a distal portion 66 having a distal end 68. Proximalportion 62 comprises a handle 70. Handle 70 is configured to assist ingrasping and manipulating guidewire directing device 60. The distalportion 66 comprises a shaft 72 having a fork-tipped end 68. Guidewiredirecting device 60 engages a guidewire at the fork-tipped end 68.Handle 70 is rotated, advanced, and withdrawn, thereby altering thedirection of the advancing guidewire.

[0110] A directing sheath 100, as shown in FIG. 17, may also be providedfor assisting in aligning the guidewire or delivery catheter to passthrough bone anchors 10. Directing sheath 100 comprises a proximalportion 102, a distal portion 104, and a central portion 106. Centralportion 106 includes at least two openings 108 sized substantially thesame as portal 22 of bone anchor 10. Directing sheath 100 preferablyincludes a lumen 110 extending through its entire length. Lumen 110 isof sufficient diameter to allow a structure such as a guidewire ordelivery catheter to pass through. Directing sheath 100 may be scoredalong its longitudinal axis, on either one line or two opposing lines112. Scoring 112 allows directing sheath 100 to be split into twoseparate halves by pulling the sheath apart at its proximal or distalend. Scoring 112 can be partially or completely through the sheath wall.

[0111] Directing sheath 100 is preferably formed from a biocompatiblepolymer. Directing sheath 100 may also include a radiopaque filament 114passing around each opening in central portion 106 or the entire lengthof sheath 100. Filament 114 aids in localizing directing sheath 100after percutaneous placement.

[0112] Although the application of the present invention will bedisclosed in connection with connecting two unstable vertebrae, themethods and structures disclosed herein are intended for various otherapplications such as to connect three or more vertebrae, as will beapparent to those of skill in the art in view of the disclosure herein.In addition, the method may be used to stabilize the L5 vertebrae, usingthe cranial-ward portion of the sacrum as the vertebrae with which L5 isanchored. Furthermore, although the method is disclosed and depicted asapplied on the left side of the vertebral column, the method can also beapplied on the right side of the vertebral column, or both sides of thevertebral column simultaneously.

[0113] The method of the present invention involves percutaneouslyinserting one or more fusion devices into two or more than two adjacentvertebrae, either unilaterally or, preferably bilaterally, where aportion or all of at least one of the vertebrae is unstable, separatedor displaced. The fusion devices reposition or fix the displacedvertebra or portion of the displaced vertebra to a position within thevertebral column which is more stable or which causes less morbidity.

[0114] Referring now to FIG. 18 through FIG. 28, there are shown aseries of drawings depicting various stages of the method ofrepositioning and fixing a displaced vertebra or portion of a displacedvertebra, unilaterally, according to the present invention. FIGS. 18-28show partial cutaway, perspective, midline sagittal views of a portionof a vertebral column undergoing the method of the present invention.

[0115] The method will now be disclosed and depicted with reference toonly two vertebrae, one which is either unstable, separated or displacedand one of which is neither unstable, separated nor displaced. However,the method can also be applied to three or more vertebraesimultaneously, as will be understood by those with skill in the artwith reference to this disclosure. Additionally, the method can be usedto stabilize the L5 vertebrae, using the cranial-ward portion of thesacrum as the “vertebrae” with which L5 is anchored. Further, though themethod is disclosed and depicted as applied on the left side of thevertebral column, the method can also be applied on the right side ofthe vertebral column or, preferably, can be applied on both sides of thevertebral column, as will be understood by those with skill in the artwith reference to this disclosure.

[0116] First, the present method comprises identifying a patient who isa suitable candidate for undergoing the method. A suitable candidate hasone or more unstable vertebrae, one or more portions of one or morevertebrae at least partly separated from the remainder of the vertebrae,one or more portions of one or more vertebrae at least partly separatedfrom the remainder of the vertebrae with potential or completeseparation, or has one or more vertebrae or a portion of one or morevertebrae displaced from its normal position relative to the vertebralcolumn, or has one or more portions of one or more vertebrae at leastpartly separated from the remainder of the vertebrae and displaced fromits normal position relative to the vertebral column. Further, thesuitable candidate will preferably have either pain, loss of function orreal or potential instability which is likely due to the separation ordisplacement, or separation and displacement. If only a portion of thevertebra is unstable, separated or displaced, the portion of thevertebra that is unstable, separated or displaced will generally includeat least part of the vertebral body and adjoining pedicle. However,other unstable, separated or displaced portions of a vertebra can berepositioned or fixed using the present method, as will be understood bythose with skill in the art with reference to this disclosure. Forexample, a suitable patient can have a disease or condition such asspondylosis, spondylolisthesis, vertebral instability, spinal stenosisand degenerated, herniated, or degenerated and herniated intervertebraldiscs, though actual indications require the expertise of one of skillin the art as will be understood by those with skill in the art withreference to this disclosure.

[0117] Next, the present method comprises making a stab incision in thepatient's skin overlying the patient's vertebral column at or near thelevel of the vertebrae or portion of vertebrae to be repositioned orfixed. In one embodiment, the incision is made at or near the level ofthe pedicle of the vertebra or portion of vertebra to be repositioned orfixed. The pedicle level is located preferably by identifying thepedicle shadow using fluoroscopy. In a preferred embodiment, the stabincision is made using a #11 scalpel blade.

[0118] Then, as shown in FIG. 18, an 11-gauge bone biopsy needle 202 orits equivalent is placed through the stab incision to create a tract tothe posterior periosteal surface of the vertebra 200 which is to bestabilized, repositioned or fixed. Next, the biopsy needle 202 is usedto make a small incision in the periosteum and into the cortex of thevertebrae.

[0119] Then, as shown in FIG. 19, a rigid, needle-tipped guidewire 204having a diameter in the range of 0.035″ to about 0.060″ is insertedthough the biopsy needle 202 into the tract, through the periostealincision and into the cortex of the bone, and the guidewire 204 isadvanced into the anterior aspect of the vertebral body 200 or intoanother suitable portion of the vertebrae 200, as will be understood bythose with skill in the art with reference to this disclosure. Insertionof the guidewire 204 is preferably accomplished using fluoroscopy. Thisprocess creates a continuous tract from the skin surface into theanterior vertebral body or suitable portion of the vertebrae 200.

[0120] The biopsy needle 202 is then removed and the tract from the skinsurface to the nicked periosteal surface is enlarged by using ahigh-pressure fascial dilator balloon (not shown) over the needle-tippedguidewire. Then, the balloon is removed and a working sheath 206 isintroduced into the dilated tract. Alternately, a hard plastic ormetallic sheath with a central dilator is advanced over the guidewirefrom the skin surface to the periosteal surface. Next, a pilot hole maybe drilled using an over-the-wire drill bit driven by a hand held drill.

[0121] Next, as shown in FIG. 20, a bone screw 208 according to thepresent invention is introduced into the working sheath 206 over theguidewire 204 by introducing the central lumen of the bone screw 208over the proximal end of the guidewire 204′ A screwdriver 210 accordingto the present invention is similarly introduced over the guidewire 204.The bone screw 208 and distal portion of the screwdriver 210 are thenadvanced distally through the sheath 206 and the tract to the periostealsurface of the vertebral 200 until the proximal portion of the bonescrew 208 using is engaged by the tip of the screwdriver 210. Torque isapplied to the bone screw 208 using the screwdriver 210 and the bonescrew 208 is advanced until the distal portion of the bone screw 208enters the anterior vertebral body or other suitable portion of thevertebra 200, while the portal of the bone screw 208 is exterior anddorsal to the vertebra 200 and the portal is open parallel to the longaxis of the vertebral column. Then, as shown in FIG. 21, the guidewire204, sheath 206 and screwdriver 210 are removed after satisfactoryplacement of the bone screw 208 has been obtained and confirmed byfluoroscopy. Additionally, bone matrix material such as a hydroxyapatitepreparation can be injected into the central lumen of the bone screw andthrough the one or more than one perforation, if present, to promotebone ingrowth.

[0122] The stages discussed above are repeated for at least oneadditional vertebra 212 until each vertebra that is to be repositionedor fixed has a bone screw 208 applied, and additionally for at least onevertebra which is neither unstable, separated nor displaced and whichlies adjacent the cranial-most or caudal-most vertebra that is beingrepositioned or fixed. The bone screw 208 placed into the vertebra 212which is neither unstable, separated nor displaced is used as the anchorto reposition or fix each vertebra 200 which is unstable, separated ordisplaced as follows. As will be understood by those with skill in theart with reference to this disclosure, the bone screws can be placedinto the vertebrae in a different order to that described above.

[0123] After a bone screw is positioned in each vertebra, the portalsare connected using an inflatable connection rod according to thepresent invention where the rod is inserted between the portals of thebone screws and inflated to create a rigid structure with the bonescrews, thereby repositioning and fixing the one or more than onepreviously unstable, separated or displaced vertebra, or one or morepreviously unstable, separated or displaced portions of one or morevertebrae with the vertebra that is neither unstable, separated nordisplaced. Connection of the bone screws with the inflatable rod isaccomplished as follows.

[0124] Referring now to FIG. 22 and FIG. 23, a hollow needle 214, suchas a 16 gauge or 18 gauge needle, is inserted percutaneously andfluoroscopically advanced to the portal of one of the bone screws 208.While the hollow needle is shown engaging the bone screw 208 in thecranial-ward vertebrae 212, the hollow needle can engage the bone screw208 in the caudal-ward vertebrae 200 first, as will be understood bythose with skill in the art with reference to this disclosure. FIG. 23is a detailed view of FIG. 22.

[0125] Then, as shown in FIG. 24, a needle-tipped, semi-rigid guidewire216 is introduced through the lumen of the hollow needle 214 and intothe portal of the bone screw 208 in the cranial-ward vertebrae 212. Thehollow needle 214 preferably has a Tuohy needle tip which causes theguidewire 216 to exit the hollow needle 214 perpendicular to thedistal-proximal axis of the bone screw 208 and parallel to the long axisof the vertebral column. Alternately, the hollow needle 214 can have anangled-tip modified Ross needle or other suitable structure as will beunderstood by those with skill in the art with reference to thisdisclosure.

[0126] In one embodiment, as further shown in FIG. 24, a guidewiredirecting device 218 according to the present invention is insertedpercutaneously between the portals of each bone screw 208 and thefork-tipped end is used to direct the advancing guidewire 216 throughthe second bone screw portal, and to reorient the guidewire 216 afterthe guidewire 216 has passed through the portal on the bone screw 208 ofthe caudal-ward vertebrae 212.

[0127] In another embodiment, as further shown in FIG. 24, a guidewirecapture device 219, such as a snare or grasping forceps, is insertedpercutaneously, caudal to the portal of the bone screw in thecaudal-ward vertebrae. The capture device 219 engages the guidewireafter it passes through the portal of the bone screw in the caudal-wardvertebra and allows the distal end of the guidewire to be pulled throughthe skin posteriorly to obtain control of both the proximal and distalends of the guidewire.

[0128] In another embodiment, the needle-tipped, semi-rigid guidewire216 comprises an outer helical, flat wire sheath and an innerretractable sharp tip stylet. Once the needle-tipped, semi-rigidguidewire is placed, the stylet can be removed to allow for easiercapture by the capture device with less trauma to the surroundingtissue.

[0129] Then, as shown in FIG. 25, the entire guidewire tract is dilatedusing a high pressure balloon and a flexible introducer sheath 220 ispassed over the guidewire 216 along the entire guidewire tract exitingthe caudal-ward stab incision. The guidewire 216 is removed after theintroducer sheath 220 is placed.

[0130] Next, as shown in FIG. 26, an uninflated, inflatable connectionrod 222 according to the present invention which is attached to aproximal pushing catheter 224 is advanced through the introducer sheath220 until the inflatable connection rod 222 advances between the twoportals and the proximal end of the inflatable connection rod 222 liescranial to the portal on the bone screw 208 in the cranial-ward vertebra212 while the distal end of the inflatable connection rod 222 liescaudal to the portal on the bone screw 208 in the caudal-ward vertebra200. The sheath 220 is removed and the placement is confirmed byfluoroscopy.

[0131] Then, as shown in FIG. 27, the balloon of the inflatableconnection rod 222 is inflated with a rapid setting, liquid polymer, orits equivalent, and the polymer is allowed to set fixing each bone screw208 in relation to each other and repositioning and fixing the vertebra200 or portion of the vertebra that was unstable, separated ordisplaced. In one embodiment, the liquid polymer is or includespolymethylmethacrylate or other hardenable media such as those discussedelsewhere herein. The inflated balloon of the inflatable connection rod222 expands radially beyond the diameter of the portals of each bonescrew 208 which helps fix the bone screws 208 in relation to each other.

[0132] Finally, as shown in FIG. 28, the delivery or pushing catheter224 is detached from the inflatable connection rod 222 by pulling on thepushing catheter 224 while resisting proximal movement of the inflatableconnection rod 222 to disengage the inflatable connection rod 222 fromthe pushing catheter 224 and the pushing catheter 224 is removed. Theinflatable connection rod 222 comprises a self-sealing valve whichprevents the polymer from leaking once the pushing catheter is detached.The vertebra is then fixed unilaterally. The method can be repeated onthe opposite side of the spinous processes of the patient's vertebraecolumn, thereby repositioning or fixing the one or more unstable,separated or displaced vertebrae or the one or more portions of one ormore vertebrae bilaterally. The stable incisions are closed or sealed asnecessary and routine postoperative care administered.

[0133] Referring now to FIG. 29, there is shown a posterior perspectiveview of a portion of a vertebral column which has had some vertebraerepositioned and fixed bilaterally according to the present invention.When bilateral fixation is accomplished, it is preferred to place allbone screws before connecting the portals with inflatable connectionrods.

[0134] In another embodiment of the present method, a directing sheath300 according to the present invention is advanced over a guidewireuntil the openings in the directing sheath 300 overlie the position ineach vertebra which will receive a bone screw 208. The bone screws 208are then placed as disclosed in this disclosure, but through theopenings in the directing sheath 300, which aligns the lumen in thedirecting sheath with the portals of the bone screw 208. Then (notshown), a guidewire is then inserted into the lumen of the directingsheath at the proximal end of the directing sheath and advanced untilthe guidewire passes through each portal of the bone screws and exitsthe body through the lumen of the directing sheath at the distal end.The directing sheath is then removed by peeling the sheath apart alongthe scored lines and pulling the two halves out from the body. Theguidewire that was in the lumen of the directing sheath remains in placeto guide the placement of the uninflated, inflatable connection rod.Alternately, the uninflated, connection rod can be inserted directlyinto the lumen of the directing sheath at the proximal end and advanceduntil the uninflated, inflatable connection rod is properly positionedbetween the portals of the bone screws. Referring now to FIGS. 30through 32, there are shown posterior perspective views of a portion ofa vertebral column undergoing the method of the present invention usinga directing sheath according to the present invention, showing the bonescrews placed through the openings of the directing sheath. As can beseen in FIG. 30, the directing sheath 300 is positioned adjacent thevertebral column 302 according to the present invention. Next as can beseen in FIG. 31, guidewires 304 are used to place bone screws 306through openings 308 in the directing sheath 300. Finally, as can beseem in FIG. 32, the directing sheath 300 is removed by the directingsheath 300 into two separate halves.

[0135] In one embodiment, there is provide a kit for performing themethod of the present invention. The kit comprises a plurality of bonescrews according to the present invention. The kit can also compriseother components of the system of the present invention, such as aguidewire directing device, an inflatable connection rod, the componentsof the polymer system to be mixed and injected and a directing sheath.In another preferred embodiment, the kit also comprises a screwdriveraccording to the present invention.

[0136] Referring to FIG. 29, a first inflatable connection rod 222 a anda second inflatable connection rod 222 b are illustrated as extendinggenerally in parallel with each other, and also generally in parallel tothe longitudinal axis of the spine. Deviations from this illustratedparallel relationship may also occur, in either or both of the lateralplane as well as the anterior/posterior plane. Such deviations fromparallel may be a consequence of anatomical variations, or proceduralchoices or irregularities as will be appreciated by those of skill inthe art. In any of these configurations, additional stability may beachieved by cross-linking the first inflatable connection rod 222 a withthe second inflatable connection rod 222 b. Thus, in accordance with afurther aspect of the present invention, there is provided a method andapparatus for cross-linking two or more inflatable connection rods.

[0137] Cross-linking may be accomplished in any of a variety ofconfigurations, as will be apparent to those of skill in the art in viewof the disclosure herein. For example, a pair of laterally opposingpedicle screws 208 may be connected to each other by an inflatablecrossbar or solid crossbar as will be apparent from the disclosureherein. Alternatively, the body of the two opposing inflatableconnection rods 222 a and 222 b can also be connected by a crossbar.Although the present discussion will focus primarily upon the latterconstruction, it is to be understood that the present inventioncontemplates any cross connection between a left and right connectionrod, preferably through a procedure in which each of the connection rodsor crossbars is installed in a less invasive or minimally invasiveprocedure.

[0138] Referring to FIG. 33, a side elevational view of a portion of thespine is illustrated. A first and second pedicle screws 208 have beenpositioned in accordance with procedures discussed previously herein. Ahollow needle 214 is illustrated, for guiding a “rocketwire” orguidewire 216 through the coaxial apertures in the first and secondpedicle screws 208.

[0139]FIG. 33 additionally illustrates a cross tie deployment system230, partway through a deployment procedure. The cross tie deploymentsystem 230 comprises an access sheath 232. Access sheath 232 comprisesan elongate tubular body having a proximal end and a distal end, and acentral lumen extending therethrough. In general, the central lumen willhave a diameter within the range of from about 24 French to about 30French, although other diameters may be utilized depending upon the sizeof the device to be deployed. The access sheath 232 is positionedthrough tissue along an axis which intersects the path of the guidewire216, as is advanced from a first pedicle screw 208 through an aperturein a second pedicle screw 208, as illustrated.

[0140] A cross tie support 248 is axially movably positioned within theaccess sheath 232. Cross tie support 248 is connected at a distal end249 through a releasable connector 246 to a cross tie 234. Cross tie 234facilitates connection of a crossbar with a primary inflatableconnection rod, to achieve cross linking of the orthopedic fixationsystem.

[0141] Although a variety of structures for cross tie 234 can beutilized, one convenient construction is illustrated in FIG. 37. Ingeneral, the cross tie 234 includes a first connector 236 such as afirst aperture 238 for receiving an inflatable connection rod 222 as hasbeen discussed previously herein. In one implementation, the aperture238 has an inside diameter of approximately 6 mm. However, diameters ofthe first aperture 238 may be varied widely, depending upon the diameterof the inflatable connection rod 222, and the desired physicalperformance characteristics.

[0142] The cross tie 234 additionally comprises a second connector 240,such as a second aperture 242. The second aperture 242 is adapted toreceive a crossbar 222 c, as illustrated in FIGS. 35 and 36. In theillustrated cross tie 234, a longitudinal axis extending through thefirst aperture 238 is generally perpendicular to a longitudinal axisextending through a second aperture 242, and offset by a spacingdistance which will determine the anterior-posterior spacing between theaxis of an inflatable connection rod 222 a and a corresponding crossbar222 c. In one embodiment, the overall as mounted anterior-posteriorlength of the cross tie 234 is approximately 16 mm, and the width of thecross tie 234 is no more than about 8 mm.

[0143] The cross tie 234 is held in place during the procedure by across tie support 248 through a releasable connector 246. The releasableconnector 246 facilitates the positioning of the cross tie 234 duringthe deployment step, but enables decoupling following proper positioningof at least an inflatable connection rod 222 a and possibly also thecrossbar 222 c. Any of a variety of releasable connection structures maybe utilized, such as a threaded distal end on the cross tie support 248,which threadably engages an aperture on the cross tie 234.

[0144] As illustrated in FIGS. 33, 36 and 37, the cross tie 234 is heldin position by the cross tie support 248 such that the longitudinal axisextending through the first aperture 238 is colinear with the path ofthe guidewire 216. The longitudinal axis of the second aperture 242extends transversely such that it aligns with a second aperture 242 in asecond cross tie 234 to accomplish the cross-linked constructionillustrated in FIGS. 35 and 36.

[0145] Referring to FIG. 34, the first inflatable connection rod 222 ais illustrated as inflated after having been positioned through thefirst aperture 238 on the cross tie 234, as well as through theapproximately colinear apertures on a pair of bone screws 208. This isaccomplished by advancing the guidewire 216 through the first bonescrew, then the first aperture 238 and then the second bone screw 208,as illustrated in progress in FIG. 33. The connection rod 222 a may thenbe advanced over the wire and inflated following the inflatableconnection rod implantation procedures discussed previously herein.

[0146] Preferably, the first aperture 238 is dimensioned with respect tothe connection rod 222 a such that a secure fit is provided between theinflatable connection rod 222 a and cross tie 234 following completecuring of the curable media. If shrinkage of the curable media iscontemplated, the first aperture 238 may be defined within an annularring on the frame 244 which has an expansion break extendingtherethrough. In this manner, inflation of the inflatable connection rod222 a can be accomplished such that the expansion break allows a slightenlargement of the diameter of the first aperture 238. Upon transverseshrinkage of the inflatable connection rod 222 a during the curingprocess, the natural bias imparted by the frame 244 allows the firstaperture 238 to shrink, thereby retaining a tight fit with theinflatable connection rod 222 a throughout a range of diameters. Thisconstruction may also be applied to the apertures extending through thebone screws 208, as well as the second apertures 242.

[0147] The cross tie support 248 is illustrated in FIG. 34 as detachedfrom the cross tie 234, such as by unscrewing the releasable connector246. This may be accomplished before or after positioning of thecrossbar 222 c, depending upon the clinical judgment of thepractitioner.

[0148] The final construction is illustrated in FIG. 35. As seentherein, a crossbar 222 c extends between a first cross tie 234 carriedby the first inflatable connection rod 222 a and a second cross tie 234carried by the second inflatable connection rod 222 b. The crossbar 222c may be positioned through the pair of opposing apertures 242 using thesame techniques discussed and illustrated previously herein for theimplantation of the inflatable connection rods 222. The initial positionof a curved needle and guidewire for positioning the crossbar 222 c isschematically illustrated in FIG. 36.

[0149] Although only a single crossbar 222 c is illustrated, two orthree or four or more crossbars 222 c may alternatively be used,depending upon the axial lengths of the inflatable connection rods 222 aand 222 b, and the desired structural integrity of the finishedassembly. In addition, although the crossbar 222 c is illustrated asextending generally perpendicular to the longitudinal axis of each ofthe inflatable connection rods 222 a and 222 b, the crossbar 222 c maycross each of the inflatable connection rods 222 at any of a variety ofangles ranging from approximately +45° to −45° with respect to theillustrated position. Thus, the crossbar 222 c may be implanted at adiagonal if the desired structural integrity can be thus achieved.

[0150] The crossbar 222 c may comprise any of a variety of forms. Forexample, the crossbar illustrated in FIG. 35 may be identical inconstruction to any of the inflatable connection rods discussedpreviously herein.

[0151] In an alternate application of the cross-linking technology ofthe present invention, the crossbar is constructed in a manner whichenables elimination of the separate cross tie 234. Referring to FIGS.40-43, the crossbar comprises a first portal 250, for receiving a firstinflatable connection rod 222 a, and a second portal 252 for receiving asecond inflatable connection rod 222 b. First portal 250 and secondportal 252 are spaced apart by an elongate tubular body 254. Body 254may be a solid element, such as a polymeric extrusion, molded part ormetal rod. Alternatively, body 254 comprises a tubular sleeve, such asillustrated in FIGS. 40-42. In the illustrated embodiment, the tubularsleeve is provided with a plurality of circumferentially extending slots254, to permit flexibility of the crossbar 222 c during deployment.Slots 254 may be formed such as by laser cutting a stainless steel,nickel-titanium alloy or other tube.

[0152]FIG. 41 schematically illustrates the distal end of a deploymentsystem 258 for deploying the crossbar 222 c of FIG. 40. The tubular body254 is carried by a dilator 260 which extends axially therethrough. Inone application, the dilator 260 is approximately 21 French, foraccommodating a tubular body 254 having an inside diameter of about 7 mmand an outside diameter of about 8 mm.

[0153] The 21 French dilator 260 is advanced over a stiff 0.038″guidewire, with an 8 French catheter. A 24 French pusher sheath 262 ispositioned proximally of the tubular body 254.

[0154] Using this deployment system, the tubular body 254 may bepositioned relative to two pairs of bone screws 208 as illustratedschematically in FIG. 42. A first pair of bone screws 208 a and 208 bcontain apertures which coaxially align with the first portal 250. Asecond pair of bone screws 208 c and 208 d carry apertures which arecoaxially aligned with a second portal 252. Once positioned asillustrated in FIG. 242, a guiding assembly such as a curved needle 214and a rocket wire 216 may be advanced as illustrated in FIG. 42. Aninflatable connection rod 222 a may thereafter be advanced along thewire, and inflated to secure the first and second bone screws 208 a and208 b, and also the crossbar 222 c. A similar procedure may beaccomplished to install a second inflatable connection rod 222 b.

[0155] The tubular body 254 may by itself provide sufficientcross-linking strength for the intended purpose. Alternatively, thetubular body 254 may be filled with a curable media 266 to enhance thestructural integrity of the resulting assembly. For example, asillustrated in FIG. 43, the deployment system 258 may additionallycomprise an inflatable container such as an inflatable connection rodpreviously disclosed herein, in communication with a source of curablemedia through an inflation lumen. Depending upon the construction of theinflatable container, it may be filled with a hardenable media 266either prior to or following positioning of the first inflatableconnection rod 222 a and second inflatable rod 222 b as discussedpreviously herein.

[0156] The embodiment of FIGS. 40-43 is illustrated in position withinthe patient, in FIGS. 38 and 39. As can be seen from FIGS. 38 and 39,the crossbar 222 c resides within the plane that extends through theapertures in the bone screws 208. Thus, the crossbar 222 c in theconfiguration illustrated in FIGS. 38 and 39 is lower profile, orpositioned anteriorly of the crossbar 222 c in the embodiment of FIGS.34 and 35. The location of the crossbar 222 c in FIGS. 38 and 39 is not,however, precisely to scale or in the exact or only implantable locationin the spine. For example, the crossbar 222 c may extend laterallythrough a space inbetween an adjacent pair of caudal and cephaladspinous processes. If the crossbar 222 c is preferably positioned at amore caudal or cephalad position than the opening between adjacentspinous processes, or if the crossbar 222 c is preferably positionedfarther anteriorly than would be permitted by the transverse process orother bony structure, the crossbar 222 c may extend through an aperturebored through the bone, or portions of the bone may be removed. Any of avariety of bores or drills may be utilized to bore a transverseaperture, such as through a spinous process. The crossbar 222 c maythereafter be advanced through the bore and locked into place using thefirst and second support structure 222 a and 222 b as is disclosedelsewhere herein.

[0157] Although the present invention has been described in terms ofcertain preferred embodiments, other embodiments of the inventionincluding variations in dimensions, configuration and materials will beapparent to those of skill in the art in view of the disclosure herein.In addition, all features discussed in connection with any oneembodiment herein can be readily adapted for use in other embodimentsherein. The use of different terms or reference numerals for similarfeatures in different embodiments does not imply differences other thanthose which may be expressly set forth. Accordingly, the presentinvention is intended to be described solely by reference to theappended claims, and not limited to the preferred embodiments disclosedherein.

What is claimed is:
 1. A subcutaneously assembled in place orthopedicconstruct, comprising: a first support structure, attached to the spine;a second support structure, attached to the spine; and a cross bar,which connects the first support structure to the second supportstructure to form an orthopedic construct; wherein the cross bar isattached to the first and second support structures subcutaneously.
 2. Asubcutaneously assembled in place construct as in claim 1, wherein thefirst support structure comprises a hardenable media.
 3. Asubcutaneously assembled in place construct as in claim 2, wherein thesecond support structure comprises a hardenable media.
 4. Asubcutaneously assembled in place construct as in claim 3, wherein thecross bar comprises a hardenable media.
 5. A subcutaneously assembled inplace construct as in claim 1, further comprising a first cross tieconnecting the cross bar to the first support, and a second cross tieconnecting the cross bar to the second support.
 6. A subcutaneouslyassembled in place construct as in claim 1, wherein the cross barincludes a first aperture for receiving the first support, and a secondaperture for receiving the second support.
 7. A subcutaneously assembledin place construct as in claim 1, further comprising a first bone anchorconnecting the first support structure to a first vertebral body, and asecond bone anchor connecting the first support structure to a secondvertebral body.
 8. A subcutaneously assembled in place construct as inclaim 7, wherein the first support structure extends through an aperturein the first bone anchor.
 9. A subcutaneously assembled in placeconstruct as in claim 1, wherein at least the first support structurecomprises: an outer wall, defining a cavity therein; a plurality ofreinforcing fibers in the cavity; and a hardenable media for bondingwith the reinforcing fibers to form the support structure; wherein thehardenable media is hardened while the support structure is positionedwithin the body of a patient to create the orthopedic construct.
 10. Asubcutaneously assembled in place construct as in claim 9, wherein thehardenable media comprises an epoxy.
 11. A subcutaneously assembled inplace construct as in claim 9, wherein the hardenable media comprisespolyurethane.
 12. A subcutaneously assembled in place construct as inclaim 9, wherein the reinforcing fibers comprise carbon fibers.
 13. Asubcutaneously assembled in place construct as in claim 9, wherein thereinforcing fibers comprise graphite fibers having a diameter within therange of from about 0.003 inches to about 0.007 inches.
 14. Asubcutaneously assembled in place construct as in claim 9, wherein thereinforcing fibers are provided in at least one bundle having within therange of from about 3,000 to about 12,000 fibers.
 15. A subcutaneouslyassembled in place construct as in claim 14, comprising from about 30 toabout 60 bundles of fibers.
 16. A subcutaneously assembled in placeconstruct as in claim 9, wherein the reinforcing fibers have a Towtensile strength within the range of from about 5,000 Mpa to about 7,000Mpa.
 17. A subcutaneously assembled in place construct as in claim 9,wherein the reinforcing fibers have a Tow tensile modulus within therange of from about 250 Gpa to about 350 Gpa.
 18. A subcutaneouslyassembled in place construct as in claim 9, further comprising at leastone reinforcing sleeve within the cavity.
 19. A subcutaneously assembledin place construct as in claim 9, wherein the reinforcing sleevecomprises a braided carbon fiber wall.
 20. A method of treating thespine, comprising the steps of: attaching a first support structure tothe spine; attaching a second support structure to the spine; andattaching a cross bar to the first and second support structures;wherein at least the attaching a cross bar step comprises advancing atleast a portion of the cross bar between the spine and a muscle layer.21. A method of treating a patient, comprising the steps of: securing afirst rod at a first site in the patient; securing a second rod at asecond site in the patient; introducing a curable media in between thefirst and second rods to form a cross link; and linking the first rod tothe second rod by permitting the media to cure.
 22. A method of treatinga patient as in claim 21, wherein the introducing step comprisesintroducing the curable media into a tubular media support structureextending between the first and second rods.
 23. A method of treating apatient as in claim 22, wherein the support structure comprises aballoon.
 24. A method of treating a patient as in claim 21, wherein themethod is accomplished percutaneously.
 25. A method as in claim 21,wherein the linking step comprises positioning a balloon between thefirst and second rods and introducing the media into the balloon.